ABSTRACT Cassava has a high yield potential that can be achieved with adequate liming and fertilization of the soil. The objective of this study was to evaluate the effect of organic fertilizer application, in association or not with liming, on yield and morphological characteristics of cassava roots and on chemical and physical properties of the soil. The experiment was arranged in the split plot design. The plots corresponded to limestone rates (0 and 2.5 t ha-1) and the sub-plots to chicken manure rates (0, 4, 8, and 12 t ha-1). Yield showed no response to limestone application, but responded to manure, producing 43 t ha-1 of roots at the rate of 8 t ha-1. The treatments had no influence on soil density and total porosity. The addition of manure increased the concentrations of P and K, while the addition of limestone increased Ca and Mg in the soil. The pH was affected only by limestone. Therefore, limestone does not affect crop yield and soil physical properties up to the amount used. Use of chicken manure up to 8 t ha-1 increased yield. Limestone and manure affect soil fertility in different ways.

O objetivo deste trabalho foi verificar o efeito da substituição do fosfato pelo composto derivado fosfito no crescimento in vitro de segmentos nodais de batata doce. Os segmentos obtidos de culturas prévias foram incubados em meio MS com as seguintes combinações de fosfato/fosfito: Controle (100 / 0%); T1 (87.5 /12.5%); T2 (75 / 25%); T3 (50 / 50%) e T4 (0 / 100%) respectivamente, em arranjo fatorial de 5x5, com cinco tratamentos (Controle, T1, T2, T3 e T4) e cinco períodos de avaliação (7, 14, 21, 28 e 35 dias). O desenho experimental foi completamente casualizado com três repetições com dois explantes por período. As avaliações foram feitas semanalmente por contagem do número de brotos, comprimento e peso seco de parte aérea de brotos e raízes. O aumento da dose de fosfito diminuiu todos os atributos analisados, como velocidade de crescimento, comprimento e peso seco, significando que o fosfito não pode ser utilizado em substituição ao fosfato na cultura de tecidos de batata doce.

The main objective of this work was to verify the effect of the substitution of phosphate by its related compound phosphite on the in vitro growth of sweet potato nodal segments. Segments from a previous culture were incubated in MS media with the following combinations of phosphate:phosphite: Control (100 / 0%); T1 (87.5 / 12.5%); T2 (75 / 25%); T3 (50 / 50%) and T4 (0 / 100%) in a 5 x 5 factorial arrangement, with five treatments (Control, T1, T2, T3 and T4) and five evaluation periods (7, 14, 21, 28 and 35 days). The design was completely random, with three replicates of two explants per period. The evaluations were made weekly by counting the number of shoots and the length and dry weight of shoots and roots. Increasing the phosphite concentration decreased all attributes measured, including growth velocity, length and dry weight. These results indicate that phosphite cannot be used as substituted of phosphate in sweet potato tissue cultures.